Aircraft: WIDEBODY; LOW WING; 2 TURBOJET ENG
Phase of flight: Takeoff / Launch
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy

We were cleared to line up and wait behind landing traffic on Runway 28 for our night time departure. After a normal delay; during which the landing aircraft disappeared from view; we were cleared for takeoff. As we rolled down the runway I became suspicious that the lights we believed were the runway edge lights were in fact the lights of another aircraft. At about 130 knots I was reasonably certain the lights were in fact a second aircraft; parked or taxing slowly; at the end of the runway. The clues to my analysis were a shift in the position of two of the lights relative to the other edge lights; and the fact that I did not see an aircraft on the parallel taxiway. Runway 28 is over 13;000 feet long; we would normally rotate well in advance of Taxiway BB; and be airborne before reaching the 10;000 foot point of the runway. Accordingly; I realized that a high-speed abort within 10 to 15 knots of V1 was not an option; and that we would clear the aircraft by a significant margin; if indeed another aircraft was even at the end of the runway. As my First Officer rotated; and we became airborne; I looked downward and could see an aircraft apparently parked on the end of the runway. After attaining a safe altitude I returned to the Tower frequency; while the First Officer monitored the departure frequency. I first confirmed we had in fact been cleared for takeoff. I next inquired whether there was an aircraft on the end of the runway. The Control Tower clearly did not believe there was another aircraft on the runway; but then queried the aircraft in question. They replied to the Tower to apologize to us. [Two other flights] confirmed the aircraft was in fact on the end of the runway during our takeoff from Runway 28. We were departing SBGL and I was the pilot flying. We had taxied to the holding point for Runway 28 and had held there for several minutes. Tower gave us the following instruction: 'after preceding aircraft has landed; cleared to line up and wait Runway 28'; which we did. I looked downfield at this time and did not see any moving lights etc. that would indicate an aircraft still on our runway. We were then cleared for takeoff and began the takeoff roll. The initial part of the takeoff was normal; however at some point above 100 knots I heard the Captain remark that he thought there was still an aircraft at the end of our runway. I glanced up but could not distinguish anything out of the ordinary; and continued the takeoff roll and rotation. Nothing about our takeoff roll and rotation was non-normal. Upon rotation; I was able to see farther down the runway; and now could clearly see that there was indeed an aircraft at the end of Runway 28; I couldn't tell if he was parked or moving; as he disappeared from view very quickly. Separation was not an issue for us; but could certainly have been so if we had had to perform an abort. After takeoff; the Captain had me monitor the departure freq and called the Tower back; and both the Tower and another Air Carrier flight confirmed that there was an aircraft that had landed and not vacated the runway prior to our being cleared for takeoff; and that crew apologized to us over the Tower frequency. Three experienced; rested crew members were not able to identify that there was an aircraft at the end of our runway upon receiving a takeoff clearance. We had been cleared for takeoff; and did not see any moving lights etc; that would normally have given us a clue that there was still an aircraft on the runway. The Tower should not have cleared us for takeoff without being unequivocally certain that the preceding aircraft had vacated the runway. I commend the Captain; for his excellent judgment and decision to continue the takeoff rather than abort. This was a dynamic; time-compressed situation; and he reacted; I think; in the best interest of our entire crew and passengers. As it was; we were not close to the offending aircraft; but had we aborted; close to V1; things could have turned out very differently. Air Carrier flight crew reports being cleared for a night takeoff at SBGL then noticing an aircraft at the far end of the runway just prior to V1. The Captain elects to continue the takeoff and easily clears the other aircraft. The Tower Controller was speaking Portuguese to the local pilots and English to this U.S. crew.